Abstract: A piston is manufactured with functional recesses (6, 7, 8) thereof formed from property improving material (18b, 18c, 18d). A blank (10) defines a mounting recess (12, 14, 16) and a quantity of said property-improving material (18b, 18c, 18d) is secured within said mounting recess. Said functional recess (6, 7, 8) is machined out of said quantity of property-improving material. The process for securing said property-improving material (18b, 18c, 18d) comprises forming a rod (20, 22, 34) from a material which on plasticisation under heat and pressure forms said property-improving material, inserting an end of the rod into said mounting recess, and rotating said rod in contact with a surface of the mounting recess (12, 14, 16), while applying force to the rod to feed it into the mounting recess.

Abstract: A piston for use in an internal combustion engine is manufactured by forming a blank (10, 50, 70) from a first material, providing a region (20, 60, 80) of a second material in a surface portion (12, 52, 54) of the blank (10, 50, 70), the second material being secured to said first material, and forming a recess (14, 28, 56, 68, 86) so that the recess has a bounding surface at least part of which is formed by the second material.